冷凝式空气加热器回收燃天然气锅炉排烟余热的分析

文章对用空气来回收燃气锅炉排烟中水蒸气汽化潜热的冷凝式空气加热器，以加热器内烟气中的水蒸气开始冷凝处的烟气和空气的温差△tx为变量，计算分析了锅炉最终排烟温度、加热的空气量、空气回收的热量、锅炉热效率与加热器面积大小变化的关系，为选择利用空气来回收燃气锅炉汽化潜热提供理论依据。以陕北天然气为例，如果将30℃的空气加热到120℃，计算结果表明，温差出。从25℃减少到0℃时，最终排烟温度略微降低约2℃，相应的加热的空气量增大1．5倍，而加热器的面积急剧增大到无穷大，锅炉效率提高的极限为4．67％，此时潜热占总回收热量的28．6％。     

燃气锅炉烟气余热回收潜力及影响因素分析

介绍了天然气锅炉余热冷凝回收原理,分析了天然气燃烧产物的组份,提出了烟气显热和潜热的计算方法,并以燃气蒸汽锅炉为研究对象,对不同设计温度下烟气余热回收潜力进行了系统的分析计算,并对烟气余热回收影响因素进行了定量分析。结果表明,烟气中可回收的水蒸气潜热可使锅炉热效率提升10%以上,排烟温度越低,回收热量越多,锅炉热效率提升的幅度越大,但追求过低的排烟温度则会导致回收成本的增加。     

冷凝式燃气锅炉的冷凝热回收研究

冷凝燃气锅炉由于充分回收了烟气中的显热和水蒸气的凝结潜热,使燃气锅炉的热效率大幅提高,而冷凝热的回收关键在于冷凝率,其与烟气的成分、排烟温度以及空气系数有关。从理论和实验上研究了排烟温度对冷凝率的影响,并对燃气锅炉进行了正反平衡测试。研究结果表明,天然气锅炉烟气中水蒸气的理论含量在15%～18.6%之间,随过量空气系数的增加而减少,冷凝率随排烟温度的降低而逐渐增加,同温度下低的过量空气系数有高的冷凝率。理论上全部回收冷凝热时,锅炉效率可以提升的极限值为10.74%,加装了翅片管式冷凝式二级节能器后,运行监测锅炉热效率提升5%。     

天然气锅炉烟气冷凝热能回收的研究

通过理论分析与实验研究,得到烟气冷凝的特点,采用耐腐蚀材料和低阻力设计,利用锅炉给水或其它用水冷却天然气锅炉的排烟实现部分水蒸汽冷凝,降低锅炉排烟温度,回收物理显热的同时,回收部分汽化潜热,利用高低位发热量差的能量,提高天然气锅炉热效率5％以上,同时,降低NOX的排放,节能与环保效益显著。     

排烟中水蒸气汽化潜热的回收与燃油燃气锅炉热效率的改善

锅炉的热效率在很大程度上取决于排烟热损失的大小。把排烟温度降至水露点以下 ,不仅可以减少排烟中不凝气体的显热 ,而且可以回收排烟中水蒸气的潜热 ,因而能大幅度减小排烟热损失和提高锅炉热效率。燃油燃气锅炉排烟中水蒸气含量比较多 ,热效率改善效果更显著。但必须采取适当的措施防止凝结下来的硫酸和亚硫酸对低温受热面的酸腐蚀。     

燃气锅炉尾部烟气余热回收冷凝型节能器的实验研究

针对常规节能器不能有效回收燃气锅炉尾部烟气中水蒸气凝结所释放的汽化潜热、节能器系统阻力大等问题,介绍了一种低阻燃气锅炉尾部烟气余热回收冷凝型节能器的结构和实验研究情况,研究了液气比与锅炉排烟温度的关系、锅炉热效率与排烟温度的关系和节能器系统阻力与烟气流速的关系.     

燃气锅炉烟气余热回收实验分析

通常燃气锅炉的排烟温度较高 ,一般在 16 0～ 2 4 0℃。所排烟气中含有不凝结气体和水蒸气 ,过热状态的水蒸气是烟气中热量的主要携带者。文章分析了烟气成分、换热机理 ,通过实验证明了降低锅炉的排烟温度回收烟气中水蒸气的显热和潜热 ,不仅提高了锅炉的热效率 ,同时凝结液也回收了烟气中部分酸性气体 ,因此具有节能与环保的双重功效     

降低燃气锅炉排烟热损失方法探讨

燃用天然气的锅炉其排烟温度较高，除带走大量显热之外，烟气中还存在大量水蒸汽的潜热，若将这两部分热量充分回收，则将大幅度提高锅炉热效率。文章在对天然气的燃烧特性计算的基础上，分析燃气锅炉烟气潜热回收的效果和需要解决的问题。     

新型燃气锅炉尾部烟气余热回收节能器的应用研究

针对常规节能器不能有效回收燃气锅炉烟气中水蒸气凝结所释放的汽化潜热、系统阻力大等问题,介绍了一种新型低阻燃气锅炉尾部烟气余热回收节能器的结构和实际应用研究情况,分析了影响节能器换热效果的主要因素,研究了液气比与锅炉排烟温度的关系、锅炉热效率与排烟温度的关系和节能器系统阻力与烟气流速的关系.     

蓄热式燃烧技术在冷凝式燃气锅炉上的应用

天然气等碳氢燃料燃烧后的烟气中合有大量水蒸气,将排烟温度降低到水蒸气冷凝温度以下可回收水蒸气的冷凝潜热,锅炉热效率按低位发热量计算可超过100％.热平衡计算结果显示可以用助燃空气回收烟气的冷凝潜热,但烟气进口温度有一个上限值.将蓄热式燃烧技术用于燃气锅炉,可将烟气温度降低到冷凝温度之下.换向周期越短热效率越高,换向周期20 s时热效率可达106.7％.通过空气分级燃烧可以使烟气中NOx排放水平降低到46 mg/m3 (6％O2)左右的水平,且烟气冷凝液可吸附烟气中约14.3％的NOx.     

小型锅炉烟尘测试时锅炉出力的计算

锅炉烟尘测试时,必须对锅炉出力进行测试。但监测中,许多小型锅炉往往不具备相关的计量装置和仪表,为解决这一问题,文章提出了用烟气量和空气过剩系数来计算锅炉的出力的公式,在实际使用中,该方法简单易行,其结果和实测值具有很好的一致怀。     

Unerroric of control of mutual compliance of the efficiency of hydrogen engines of unmanned vehicles in the conditions of mass production

The issues related to the reliability of hydrogen engines of unmanned vehicles and increasing the efficiency of using hydrogen as fuel when using the method of its production during the decomposition of hydrogen-containing molecules of liquid-phase organic compounds in a plasma discharge under the action of intense ultrasonic exposure are considered. Experiments have shown that as a result of decomposition in the acoustoplasma discharge of liquid hydrocarbons, solid-phase carbon-containing products are formed, chemical transformations occur in the liquid phase and hydrogen-containing combustible gas is formed. Hydrogen-containing gas can be used as fuel immediately after synthesis, i.e. it does not require separation, since in addition to hydrogen it contains only impurities of CO₂ and water vapor. The purpose of the study is to formalize the basic conditions for tightening the control of mutual compliance with the efficiency of hydrogen engines of the same series in the conditions of their mass production. Methods of mathematical statistics and hardware-software modeling were used in the study. The term “unerroric of quality mutual compliance control” is introduced to describe a set of hardware and software tools for such control. The principle of in-depth testing of the technical condition of such engines of one series is described in a multidimensional formulation of the quality control problem for three of their operating parameters at once. The conditions for increasing the mutual correspondence of the measured values of such parameters in the conditions of serial production of hydrogen engines are formalized.     

中国煤炭地下气化技术的发展

本文综述了煤炭地下汽化技术的国内外发展现状,对我国“长通道、大断面”煤炭地下气化新工艺给予了技术经济评述,并提出了发展煤炭地下汽化技术的政策建议。     

Review of theory of distortion and disintegration of liquid streams

Linear and nonlinear analyses of the instabilities and distortion of liquid streams injected into a gaseous media are discussed. The various fundamental mechanisms and the predictive capabilities for the distortions are emphasized. Round jets, planar sheets, annular sheets, and conical sheets are discussed in detail. The balance between capillary and inertial forces is primarily examined. The method for simplifying the analyses in the case of thin liquid sheets is discussed. The capabilities for representing the droplet size distribution that follows the stream disintegration are outlined.     

MgO膨胀剂细度对MgO水化和水泥浆体膨胀的影响

基于《水工混凝土掺用氧化镁技术规范》中的Ⅰ型氧化镁（MgO）,研究了该型MgO膨胀剂（MEA）细度对掺粉煤灰水泥浆体膨胀性能的影响。即采用X射线衍射分析(XRD)及同步热分析（TG DSC）分析了掺MEA水泥浆体中MgO的水化性。结果表明,养护温度相同时,MEA的细度对水泥浆体内MEA中MgO的水化和水泥浆体的膨胀无显著影响,产生的膨胀均能补偿水泥浆体的收缩;MEA的细度可从试验设计采用的45 μm筛筛余15%左右增加到30%左右,这将有利于MEA生产企业的节能降耗。     

机车车轮多轴疲劳强度安全评定的研究

使用ANSYS8.0软件对高速列车车轮进行了三维有限元分析,计算出车轮在直线、曲线和道岔条件下牵引、制动共6种工况时孔边薄弱部位的应力,分别通过Mises等效平均应力方法、Sines平均主应力方法和应力分量中考虑平均应力方法计算出应力在极值位置时的等效应力幅、等效平均应力,从而进一步算出车轮的安全系数,对其疲劳强度进行评定,并对3种方法进行了比较研究。     

Constructal optimization of the geometry of an array of micro-channels

This paper documents the geometric optimization of an array of circular and non-circular ducts. The optimization was carried out numerically using finite volume method. As optimal dimensions were independent of the array configuration, the numerical simulation was performed on a unit cell. Numerical optimization for circular, square and isosceles right triangle cross-sections of channels was performed. Based on the results of this investigation, some correlations were proposed to predict the optimal hydraulic diameter and dimensionless heat transfer per unit volume. In addition to examining the effect of pressure drop on these parameters, it was showed that among the different geometries of this study, square cross-section has the most efficiency for a given volume. The numerical results of the present study were compared with approximate results reported in the literature which a good agreement was observed.     

固体热辐射Yong性能分析

本文对漫灰均温物体在常物性条件下对外辐射传热的Ｙｏｎｇ值计算建立了数学模型。通过与物体内能Ｙｏｎｇ公式的数值计算比较,得出了辐射能量的Ｙｏｎｇ值不大于内能Ｙｏｎｇ值的结论。从初步的热射Ｙｏｎｇ值计算公式发现。Ｙｏｎｇ与物体表面辐射率有关。     

Measurements of concentration distribution of hydrogen jet using deflection of center of the laser spot

The main purpose of this work is to propose a new method to evaluate the concentration distribution of the hydrogen jet by using a He–Ne laser through the jet. This research attempts to apply the expression of concentration Gaussian distribution, the refraction formula of inhomogeneous refractive index medium, and the concentration inversion function to disclose the displacement of the center of the laser spot at different heights in the gas jet. The spot images of the laser beam passing through the gas jet at three vertical heights z = 10d, 20d, 30d, and different radial positions are obtained. The radial spatial asymmetry of the gas jet is also found in the experiment. Finally, the calculated concentration distribution curve and the fluent simulation curve, it is found that the two results are very similar. Our findings show that the error between the concentration distribution of this method and the simulated concentration distribution reaches 2.43%.     

Heat of vaporization of mixtures

General expressions for the heat of vaporization of mixtures at constant pressure; at constant temperature; and at constant pressure, temperature, and composition are proposed. The last one is related to the liquid-vapor interface where steady vaporization or condensation is taking place. Numerical examples by the proposed expressions are shown for binary mixtures of HCFC22(R22) and (HCFC123(R123) © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(1): 12–24, 1996